Work will be continued on purification of the primary intracellular serine protease of Bacillus subtilis. Investigations will include comparative immunological studies with Bacillopeptidases E and F, ability of the enzyme to digest purified, sensitive enzymes, identification of digestion products, and effect of protease inhibitors on the in vivo action of the enzyme. Protease negative mutants will be screened for using newly synthesized thiolester substrates.